You’ve got the world by the tail on a downhill drag.

My parents would say that to me when I was whining about insurmountable obstacles in life or taking considerable blessings for granted.

That aphorism comes to mind this week as a bill that would make it easier for workers to unionize loses momentum. The slowdown is due in part to Democrats and their organized-labor allies, who had the political world by the tail on a downhill drag after the election but now face an incline when it comes to getting the so-called card-check bill passed.

The primary provision in the legislation would allow employees to form a union when a majority of them sign cards authorizing one. It would effectively eliminate the ability of companies to demand a secret-ballot election supervised by the National Labor Relations Board.

It is the top priority of organized labor, which has seen its numbers dwindle to 7 percent of the private sector and 12 percent of the total workforce. Unions have rightly claimed credit for President-elect Barack Obama’s decisive Electoral College victory, especially in the industrial Midwest.

Following the election, unions had a gleam in their eye about card check. They were predicting quick action on Capitol Hill, which is dominated by Democrats, and enthusiastic support from Obama.

Unions may still get what they want on the bill, but the process has become more difficult. First, it may fall to a lower rung on Obama’s agenda as he first addresses the recession.

A more recent problem involves allegations that Illinois Gov. Rod Blagojevich tried to sell to the highest bidder the Senate seat that Obama is vacating.

As my colleague Jeremy Smerd reported, a buyer Blagojevich allegedly hoped to entice was the Service Employees International Union, a vociferous advocate for card check. Blagojevich hoped to get himself appointed to a lucrative position with Change to Win, the coalition of seven unions led by the SEIU, in exchange for putting a strong card-check backer in Obama’s seat and presumably getting Obama to move card check up the White House’s legislative agenda.

This overreach by Blagojevich—and implicitly by SEIU—may set back the effort to get the bill passed. First, the whiff of scandal could foul the atmosphere surrounding card check.

Look for the bill’s opponents to take advantage of the scandal. A spokesman for the U.S. Chamber of Commerce’s Workforce Freedom Initiative says it’s too soon to tell how things will shake out. But the tremors could be sizable.

“It’s a potential sea change,” Justin Hakes says.

And it’s not just a matter of atmospherics. There is the practical matter of replacing Obama. The Democrats currently have a 58-41 lead over Republicans in the Senate, with one race undecided.

Under the chamber’s rules, 60 votes are needed to stop a filibuster, which killed card check in 2007, when Democrats had a 51-49 advantage and fell short by a handful of votes.

Now there are two seats still in play—in Illinois and Minnesota. Sen. Norm Coleman, R-Minnesota, is maintaining a slim lead in the recount of his race. If he wins, the Democratic advantage slips to 58-42.

Following the Blagojevich scandal, Democrats are calling for a special election to replace Obama. That would likely keep his seat open for a while, dropping the Democratic total to 57. For Republicans, an open seat is as good as a Republican pickup when it comes to preventing passage of the card-check bill in the first 100 days of the Obama administration.

It is improbable that a Republican would win a special election in Obama’s home state. But that’s a better chance than impossible, which was the case when the Democratic governor was poised to make the appointment.

Consider this: What if the Republicans choose a candidate who has high statewide name identification and who wouldn’t have to introduce himself to Illinois voters over the course of a few short weeks? What if that candidate was able to convince voters, as Georgia Sen. Saxby Chambliss did a week ago in his runoff, that Senate Republicans are the only check on Democratic power in Washington? What if the Illinois candidate ran against a Democrat who is tainted by Blagojevich having tried to broker a deal for him or her?

I don’t know much about Illinois politics. But if state Republicans could convince former House Speaker Dennis Hastert or former Gov. Jim Edgar to run, they might make the special election competitive.

Organized labor still has a significant lead in pushing the card-check bill. But now that momentum may be slowing over Obama’s seat.

“It could delay or prevent a vote on the bill, depending on how long the delay is and what other political priorities are addressed first,” Hakes says.

I took you on a bit of a detour through politics in this post. It was important, though, in illustrating that Democrats may face an uphill card-check battle.